17M7972N_Geotechnical_Letter_of_Results_FS_191-H.PDF

17M7972N Page 1 of 7

September 10, 2018 TPT Project 17M7972N

Martha Alunkal, PE

WSP USA

13530 Dulles Technology Drive, Suite 300

Herndon, Virginia 20171

Re: Letter of Results and Recommendations

DSR FS 191-H

Culvert Replacement and Roadway Reconstruction

Town of Namakagon, Bayfield County, Wisconsin

Dear Ms. Alunkal:

This letter presents the results of our field exploration performed at the culvert crossing Forest Road

(FR) 191 (Pioneer Road) at Taylor Creek in the Town of Namakagon, Bayfield County, Wisconsin. The site is located around 2,100 feet east of the intersection of County Highway D with FR 191 (Pioneer Road).

This work covers DSR FS 191-H as part of the WI ERFO FS 2016-1(5) project.

Project

It is our understanding that WSP USA is in the design process for culvert replacement and roadway reconstruction at the above referenced site. It is our understanding that the culvert sustained damage from a large rain event in July 2016. Based upon preliminary designs the replacement culvert will consist of a 120 inch diameter arch or elliptical pipe culvert. As part of the design process geotechnical services were requested.

Our scope of services for this project consisted of performing one (1) Standard Penetration Test (SPT) boring to a depth of 20 feet below river bottom or refusal. We were authorized to proceed with the proposed scope of services in a signed subcontractor agreement dated February 26, 2018.

Field Exploration

Field procedures for this project were performed on July 18th, 2018 using our Geoprobe Systems 7822DT track mounted drill rig and hollow stem auger drilling methods. Boring FS 191-S4 was performed to the east of the existing culvert to a depth of 19 ½ feet. Sand blowup was encountered at a depth of 19 ½ feet and the boring was terminated at this depth. The boring location is shown on the Boring Location

Sketch attached to this letter. Surface elevations were recorded by our field crew using a surveyors level and rod and were referenced to the top of the south end of the existing culvert. An elevation of 100.0 feet was assigned to this benchmark.

1301 N 3 rd St. Superior WI 54880 715 - 392 - 7114 1 - 800 - 373 - 2562 F 715 - 392 - 7163 www.twinportstesting.com

17M7972N Page 2 of 7

Laboratory Testing Results of the field testing and observed subsurface conditions were evaluated to develop a laboratory testing program. The final laboratory testing program included visual classification by a geotechnical engineer and water content testing.

Laboratory water content testing was performed in general accordance with ASTM D2216 on collected samples from the field exploration. Results of water content tests are shown on the borings logs in the

Appendix.

Subsurface Conditions - Soil

Fill soils consisting of silty sand (AASHTO A-2-4) were encountered at the surface to depths up to seven feet. Fill soils generally contained gravel, ranged from fine to coarse grained, were brown in color, and were moist.

Stratigraphic

Peat soils (AASHTO A-8) were encountered below the fill soils to a depth of nine feet. Peat soils contained sand, organics, roots, and fibers. Peat soils were generally dark brown in color and were waterbearing.

Native silt soils (AASHTO A-4) were encountered below the peat soils to a depth of 14 feet. Silt soils contained fine sand, were brown to dark brown in color, and were waterbearing. Based upon SPT N-values native silt soils appear to range from very loose to loose in relative density.

Native poorly graded sand with silt soils (AASHTO A-1-b) were encountered below the silt soils to the boring termination depth of 19 ½ feet. Poorly graded sand soils were generally fine to coarse grained, were brown in color, and were waterbearing. Based upon results of SPT N-values native poorly graded sand soils appear to be generally loose in relative density.

Subsurface Conditions - Groundwater

Groundwater was encountered in Boring FS 191-S4 at a depth of around eight feet while drilling and sampling at this site. Groundwater levels at this site are anticipated to correspond with the surface level of the adjacent Taylor Creek which had a surface elevation of 95.5 feet during field procedures.

Design Considerations and Recommendations Culverts bearing on aggregate bedding or spread footings appear to be the most economical options for this site. Alternative structure options for this site include bottomless arches or bridges bearing on spread footings.

Site Preparation

Field explorations at this site encountered fill soils at the surface to depths of about seven feet and peat soils to depths up to nine feet. The conditions and compactive effort under which fill soils were placed is unknown and it is possible that these soils would settle significantly when loaded. Peat soils are considered highly compressible and are not suitable for support of structures. Peat soils should be completely removed as outlined below.

17M7972N Page 3 of 7

Although soils beneath new construction are expected to experience little to no increase in net stresses, we do not recommend placing shallow foundations over uncontrolled fill soils or peat soils. We recommend stripping all surface fill soils, peat soils, and any organic soils encountered within the footprint and influence area (1H:1V out from the outside edge of footings or aggregate bedding) of the proposed foundations and replacing with compacted engineered fill to reach design elevations. It is our understanding that design plans by WSP show a two foot overexcavation below proposed culvert bottoms. We recommend that excavations for the placement of culverts should be excavated to a minimum depth of two feet below the bottom of culvert elevation and replaced with compacted engineered fill to reach design elevations.

Minimum excavations for the removal of fill soils and peat soils at this site are expected to be about nine feet plus two additional feet. Excavations should be observed by a geotechnical engineer or designated representative prior to the placement of engineered fill or aggregate bedding for culvert construction.

Shallow Foundations It appears that shallow foundations, consisting of spread footings or culverts bearing on aggregate bedding, may be used for foundation support when bearing on native silt/sands or engineered fill over native silt/sands. It is expected that culverts will be placed on a minimum of six inches of aggregate bedding overlying native soil. Recommendations for foundation design are provided below.

Net Allowable Bearing Stress

Results of the field and laboratory testing program were used to evaluate the net allowable bearing stress for shallow foundations. In our opinion, a net allowable bearing stress (with a minimum factor of safety of at least 2.5) of 2,000 psf (pounds per square foot) may be used to design footings placed on native soils or engineered fill over native soils.

Settlement Estimate

For foundations bearing on native soils or engineered fill over native soils and designed according to the net allowable bearing stresses outlined above, we estimate total settlement of less than one inch and differential settlements less than one-half inch.

Frost Protection We recommend that culvert foundations be placed at a minimum depth of six feet below finished exterior grade (surface of soil directly above foundation) to provide frost protection. We also recommend that roadway surface be a minimum of five feet above the water table to minimize frost heave.

In areas where new culvert construction tie into existing roadways, we recommend that excavations extend from the bottom of culverts at a slope of 1:20 (Vertical:Horizontal) to provide frost differential protection.

Backfill and Fill A wide variety of materials can be considered as suitable for engineered backfill placed in a controlled manner or for general fill soils at non-structural locations. The choice of materials is a function of structural requirements, water table conditions, seasonal construction constraints, placement and compaction methods, and other site or project specific needs. Soils which classify as SP, SP-SM, or SM in the Unified Soil Classification System (ASTM D2487) or AASHTO A-1 and AASHTO A-2 in the AASHTO Soil Classification System are usually the most available suitable soils for engineered backfill and fill.

17M7972N Page 4 of 7

For this project, we recommend that Aggregate Bedding meeting the gradation outlined below for direct culvert support/bedding.

17M7972N Page 5 of 7

Table 2: Gradation for the entire sample

Sieve Percent Passing by Weight (%)

1 ¼ inch 100

No. 4 25-100

Table 3: Gradation for the portion of the sample passing the No. 4 sieve, conform to the following limits

Sieve Percent Passing by Weight (%)

No. 4 100

No. 40 --

No. 100 0-30

No. 200 0-15

Other gradations for backfill of over excavations or embankment construction may also be suitable as approved by the project geotechnical engineer. Existing fill and native soils may be suitable for re-use, but should be verified through sieve analysis of representative bulk samples.

We recommend that a geotextile fabric (WisDOT Type SAS or equivalent) be placed between native soils and engineered fill/aggregate bedding to promote drainage and provide separation.

Compaction Standard We recommend using ASTM D698 - Standard Proctor as the laboratory compaction standard.

Density

We recommend compacting each lift to a minimum of the following percentage of the above compaction standard for the respective types of fill materials:

Table 4: Compaction Recommendation

Type of Engineered Fill % Minimum Compaction

Foundation Structural Backfill 98%

Aggregate Bedding 98%

Non-structural Foundation Backfill 95%

Within 3 Feet of Pavement or Aggregate Base Section 100%

Lift Thickness Place engineered backfill and fill materials in lifts not to exceed eight inches in a loose condition, unless the contractor can demonstrate satisfactory results when placing thicker lifts. Maximum compacted lift thickness should not exceed 12 inches in a loose condition.

Moisture In general, granular fill materials should be placed and compacted within two percent of optimum moisture content, as determined by the above referenced compaction standard. When the moisture content of fill materials is not in this range, compaction to the required density may be difficult if not impossible. The excavating contractor is responsible for controlling and adjusting moisture content of backfill materials.

Scour and Riprap We recommend the use of concrete end treatments (headwalls and wingwalls) combined with riprap to prevent the erosion of embankment soils and to provide protection against scour. Culvert foundations should be placed at an adequate depth to avoid scour. A detailed scour analysis was not included in our scope of work.

17M7972N Page 6 of 7

Dewatering Groundwater was observed in Boring FS 191-S4 at a depth of around eight feet during drilling and sampling at this site. Groundwater within excavations for construction of the proposed culvert is expected to be directly related to the levels of the adjacent Taylor Creek. If excavations extend below the groundwater surface and dewatering is necessary for construction, a large scale dewatering plan will be required. Dewatering options include diverting Taylor Creek around the excavations or installing temporary sheet pile cofferdams with sumps and pumps.

Over Sizing Excavations for the placement of engineered backfill should extend horizontally at least a minimum of one foot beyond the bottom edge of footing for every one foot of over excavation depth required below the footing.

Temporary Shoring Temporary shoring of excavations may be required for this project. Any temporary shoring systems should be designed by a registered professional engineer.

Frozen Materials If construction occurs during temperatures below freezing, the base of all excavations and backfill materials should be protected from freezing. Excavated surfaces which become frozen should be completely thawed prior to placing backfill, concrete, or pavements. If freezing has loosened and reduced the bearing capacity of the excavation surface, remove the frozen material to the undisturbed surface. Frozen material should not be used as backfill.

Observation - Excavations Excavation bottoms and engineered fill operations should be observed by a geotechnical engineer or a designated representative to assure that the recommendations in this report are being followed. In-place density testing should be performed to document that project specifications are met.

Observation - Foundations Installation of foundations should be observed and documented by a qualified technician or engineer.

We recommend that at a minimum, concrete be tested for air content, temperature, slump, and compressive strength.

Frequency of Testing For this project, we recommend a minimum density testing frequency of one test per 1,000 square feet of backfill area per lift. If the project area is smaller than this, we recommend a minimum of one test per lift. For isolated locations or questionable areas, we recommend a minimum of one test per occasion.

17M7972N Page 7 of 7

General

If you have any questions regarding our results, or if we may be of further service on this project, please call us at 715.392.7114.

Twin Ports Testing II, Inc.

Brett Carlson, PE

Project Engineer

Martin L. Halvorson, PE

Senior Engineer

Attachments:

Boring Location Sketch (1 Page), Boring Log (1 Page), Boring Log Notes (2 Pages)

N

Approximate Boring Location

DRAWN BY: CHECKED BY:

DATE: SCALE:

DRAWING NO:

TPT PROJECT NO:

DRAWING NO:

1/1

REV:

BMC MLH

7/20/2018 N/A

17M7972N-01

17M7972N

A

BORING LOCATION SKETCH

DSR FS 191-H

Town of Namakagon

Bayfield County, Wisconsin

T win

P orts

T esting

FR 191 (P

oineer R oad)

FS 191-S4

Taylor C reek

SS

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

4.0

9.0

14.0

18.0

23.0

26.0

(FILL) Silty Sand with gravel, pieves of wood, fine to coarse grained, brown, moist Percent passing #200 sieve test performed at 1 foot = 20.9 %

(FILL) Silty Sand, trace gravel, fine to coarse grained, brown, moist to wet

(FILL) Silty Sand, trace gravel, trace organics, fine to coarse grained, brown to dark brown, wet

(PT) PEAT and Buried Wood, dark brown, wet (AASHTO A-8)

(OL) ORGANIC SILT, trace sand, dark brown to greyish brown, waterbearing, loose (AASHTO A-8)

(SP) POORLY GRADED SAND with Gravel, fine to coarse grained, brown, waterbearing, medium dense (AASHTO A-1-b)

Boring then backfilled with bentonite End of Boring

CLIENT:

DSR FS 191-H

PROJECT:

7/20/18

11.5 ft WD

River Elev 1463.6 ft

Autohammer

CAVE IN LEVELWATER LEVEL

SITE LOCATION:

WSP USA

RIGSPT HAMMER

None Encountered

BORING STARTED

CREW CHIEF

MLH

WATER LEVEL

WSP USA Town of Namekagon, Bayfield County, Wisconsin

ARCHITECT - ENGINEER:

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES

IN-SITU, THE TRANSITION MAY BE GRADUAL.

05/16/18 05/16/18

REPORT DATE:

7822DT

WATER LEVEL BORING COMPLETED ABBREVIATIONS: ACR-After Casing Removal, BCR-Before Casing Removal, AB-After Boring, WD-While Drilling, WS-While Sampling, NE-None Encountered, DB-Diamond Bit, HSA-Hollow Stem Auger, RB-Rock Bit, SS-Split Spoon, ST-Shelby Tube, PA-Power Auger, MR-Mud Rotary, CS-Continuous, RP-Rock Probe, PH-Percussion Hammer, WL-Water Level, WOH-Weight of Hammer, EIL-Exceeds Instrument Level, TS-Topsoil, PP-Pocket Penetrometer

17M7972N

SA

M

PL

E

N O

D

EP

TH

(f t)

EL

EV

AT

IO

N

(f t)

0.0

10.0

20.0

30.0

1472.4

1462.4

1452.4

1442.4

SA

M

PL

E

D

IS

TA

N

C E

PLASTIC

LIMIT %

TPT Project No.:

UNCONFINED COMPRESSIVE STRENGTH (TONS/FT2)

PERCENT PASSING #200 SIEVE

10 20 30 40 50

1 2 3 4 5

10 20 30 40 50

FS 191-H (Northwest)

See Boring Location Sketch

R

EC

O

VE

R Y

10 20 30 40 50

DESCRIPTION OF MATERIAL

WATER

CONTENT %

LIQUID

LIMIT %

W

AT

ER

L

EV

EL

SA

M

PL

E

TY

PE

BORING LOCATION:

BORING LOG

STANDARD PENETRATION TEST N-VALUE

BOREHOLE LOG 17M7972N DSR FS 191 H.GPJ TWINPORT.GDT 9/10/18

G R

AP

H

IC

L

O G

SURFACE ELEVATION:

1472.4 ftST

R

AT

A C

H

AN

G E

D

EP

TH

SS

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

4.0

7.0

9.0

14.0

19.5

(FILL) Silty Sand, trace gravel, fine to medium grained, brown, moist

(FILL) Silty Sand, trace gravel, fine to coarse grained, brown, moist

(PT) PEAT with Sand, organics and roots and fibers, dark brown, wet (AASHTO A-8)

(ML) SILT with Fine Sand, dark brown to brown, waterbearing, loose (AASHTO A-4)

(SP-SM) POORLY GRADED SAND with Silt, fine to coarse grained, brown, waterbearing, loose (AASHTO A-1-b)

*2 1/2 feet of sand blow up at 19 1/2 feet

Boring then backfilled with bentonite End of Boring

CLIENT:

DSR FS 191-H

PROJECT:

7/20/18

7.9 ft WD

River Elev 95.5

Autohammer

CAVE IN LEVELWATER LEVEL

SITE LOCATION:

WSP USA

RIGSPT HAMMER

None Encountered

BORING STARTED

CREW CHIEF

JJ

WATER LEVEL

WSP USA Town of Namekagon, Bayfield County, Wisconsin

ARCHITECT - ENGINEER:

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES

IN-SITU, THE TRANSITION MAY BE GRADUAL.

07/18/18 07/18/18

REPORT DATE:

7822DT

WATER LEVEL BORING COMPLETED ABBREVIATIONS: ACR-After Casing Removal, BCR-Before Casing Removal, AB-After Boring, WD-While Drilling, WS-While Sampling, NE-None Encountered, DB-Diamond Bit, HSA-Hollow Stem Auger, RB-Rock Bit, SS-Split Spoon, ST-Shelby Tube, PA-Power Auger, MR-Mud Rotary, CS-Continuous, RP-Rock Probe, PH-Percussion Hammer, WL-Water Level, WOH-Weight of Hammer, EIL-Exceeds Instrument Level, TS-Topsoil, PP-Pocket Penetrometer

17M7972N

SA

M

PL

E

N O

D

EP

TH

(f t)

EL

EV

AT

IO

N

(f t)

0.0

10.0

20.0

103.1

93.1

83.1

SA

M

PL

E

D

IS

TA

N

C E

PLASTIC

LIMIT %

TPT Project No.:

UNCONFINED COMPRESSIVE STRENGTH (TONS/FT2)

PERCENT PASSING #200 SIEVE

10 20 30 40 50

1 2 3 4 5

10 20 30 40 50

FS 191-S4

See Boring Location Sketch

R

EC

O

VE

R Y

10 20 30 40 50

DESCRIPTION OF MATERIAL

WATER

CONTENT %

LIQUID

LIMIT %

W

AT

ER

L

EV

EL

SA

M

PL

E

TY

PE

BORING LOCATION:

BORING LOG

STANDARD PENETRATION TEST N-VALUE

BOREHOLE LOG 17M7972N DSR FS 191 H.GPJ TWINPORT.GDT 9/10/18

G R

AP

H

IC

L

O G

SURFACE ELEVATION:

103.1 ftST

R

AT

A C

H

AN

G E

D

EP

TH

N

Approximate Boring Location

DRAWN BY: CHECKED BY:

DATE: SCALE:

DRAWING NO:

TPT PROJECT NO:

DRAWING NO:

1/1

REV:

DCS BMC

7/13/2018 N/A

17M7972N-01

17M7972N

A

BORING LOCATION SKETCH

Culvert Replacement and Roadway Reconstruction

FS 191-H

Bayfield County, Wisconsin

T win

P orts

T esting

FS 191-H

BORING LOG NOTES

Water Level Water levels indicated on the boring logs are as measured at stated times. In clean sand soils, the elevations indicated are considered relatively reliable levels. However, in less permeable soils, even after several days of monitoring, accurate determinations may not be possible. Therefore, additional/alternative methods of groundwater elevation monitoring should be sought.

Commonly Used Moisture Conditions of Soils Term Meaning Dry Requires the addition of considerable moisture to attain optimum for compaction Moist Near optimum moisture for compaction Wet Requires drying to attain optimum moisture for compaction Waterbearing Saturated granular soils

Gradation Description and Terminology Soil Type Particle Name Size Range Coarse Grained Soils Boulders Over 12”

Cobbles 3”-12” Gravels #4-3” Gravels – Coarse ¾”-3” Gravels – Fine #4-¾” Sands #200-#4 Sands – Coarse #10-#4 Sands – Medium #40-#10 Sands – Fine #200-#40

Fine Grained Soils Silt 0.005 mm-#200 Clay Less than 0.005 mm

Descriptive Terms of Components Present in Sample (other than ASTM D 2487) Term Percent of Dry Weight Trace 1-5% With 5-12% Some 12-30% And 30-50%

Relative Density of Granular Soils N-Value (SPT) Relative Density Standard “N” Penetration 0-4 Very Loose Blows per foot of a 140 pound hammer 5-10 Loose falling 30” on a 2” outside diameter 11-30 Medium Dense split barrel sampler 31-50 Dense Over 50 Very Dense

Consistency of Cohesive Soils N-Value (SPT) Consistency (Q, tsf or kg/cm2) 0-2 Very Soft Less than 0.25 3-4 Soft 0.25-0.50 5-8 Medium 0.50-1.00 9-15 Stiff 1.00-2.00 16-30 Very Stiff 2.00-4.00 Over 30 Hard 4.00-8.00

UNIFIED SOIL CLASSIFICATION SYSTEM – ASTM D 2487